Safety device for refrigeration compressors



March 17, 1964 N. E. B. LARSSON SAFETY DEVICE FOR REFRIGERATIONCOMPRESSORS Filed May 15. 1961 INVENTOR. W31: 57% 6P7 a Lama UnitedStates Patent 3,125,285 SAFETY DEVIQE FOR REFREGERATEON COMPRESSORS NilsErik Birger Larsson, Finspang, Sweden, assignor to Sta] RefrigerationAktieholag, Norrkoping, Sweden, a

Swedish corporation Filed May 15, 1961, Ser. No. 110,176 3 Claims. (Cl.230-230) The invention relates to refrigeration compressors, and moreparticularly to means by which such devices are prevented from damagedue to surge.

There is the possibility in refrigeration compressors, and especially inthose of the high speed type, that fluid refrigerant may be forced fromthe evaporator into the cylinder by a surge and in such case thequantity of fluid may burst the cylinder or disc, unless some sort of aprotective means is employed. Surge is likely to occur upon starting up,when excessive boiling occurs in the refrigerator. It is known that thedisc may be provided with a spring-loaded device which allows it to liftfrom the valve seat and permit an increased flow to the compressorpressure chamber. However, such a safeguard is not always completelysatisfactory.

The present invention relates to compressors of the type provided with aspring-loaded valve disc and it is an object of the invention to makesuch compressors safer and more reliable in the event of surge. Theinvention is characterized by the fact that the valve disc is dividedinto two spring-loaded parts movable relatively to one another and tothe compressor cylinder head and which, at a surge the return platehaving pressure val es, such valves can open into the pressure chamber,allowing refrigerant to pass from the cylinder, while the otherspringloaded part can open into the compression suction chamber,permitting a return flow to the cylinder. Since the capacity of thefirst cylinder stroke to move the refrigerant is thus reduced, excessiveboiling in the evaporator is also reduced and a dangerous quantity offluid refrigerant in the compressor is avoided.

With these and other objects to be hereinafter set forth in view, I havedevised the arrangement of parts to be described and more particularlypointed out in the claims appended hereto.

The invention is illustrated in the accompanying drawings, in which thefigures there shown represent sectional views taken through the cylinderaxis, showing the upper portion of the compressor. FIGURE 1 shows thevalve disc in its normal operating position, while FIGURE 2 shows theposition of the valve disc during surge.

Referring to the drawings, 1 indicates the wall of the cylinder and 2indicates the piston movable in the usual manner within the cylinder.The valve disc, which is generally indicated at 4, is positioned in anopening in the cylinder wall and it is interposed between the top of thepiston 2 and the pressure chamber 14. The disc 4 is composed of two mainparts, one of which is indicated at 4a, and the other being indicated at5, these parts having limited movement relatively to one another. Thepart 5 constitutes a return plate for pressure valves 6 which areinterposed between the plate 5 and an apertured head 12 fastened to thepart 4a by the central bolt 16. Openings 7 are provided through theplate 5 for the passage of refrigerant.

The part 4a is in the form of a spider having an outer ring 17 connectedby spokes 18 to the central hub 19. A coil spring 9 is positionedbetween the compressor cylinder head 8 and the hub 19 of the disc 4which spring normally urges the disc to its seated position. The disc 4is movable away from seated position, as shown in FIGURE 2 and to theextent permitted by the stop ring inserted in the opening in thecylinder wall in which 3,125,285 Patented Mar. 17, 1964 ice the disc islocated. A spring shown at 11 is mounted between the return plate 5 andthe hub portion 19 of the disc 4 which spring keeps the return plate 5urged against the head 12 on the part 4. i

Normally, the refrigerant is forced by the piston 2 through the openings13 in the head 12 and past the pressure valves 6 and through theopenings 7 in the plate 5 and into the compressor pressure chamber 14.However, when a surge occurs, the return plate 5 will be lifted so thatthe refrigerant can enter the pressure chamber 14. At about the sametime, the whole disc 4- will be elevated against the biasing force ofthe spring 9 and to the extent permitted by the stop ring 10, so that anopening establishing communication between the pressure chamber 4 andthe suction chamber will be the result. A return flow of fiuid and gaspasses through such opening, and this immediately reduces the capacityof the compressor. Compressor capacity reduction thus reduces excessiveboiling in the evaporator and the compressor is relieved of any extremestresses caused by a surge.

A further and important advantage of the present construction is that bydividing the movable mass of the valve disc in the manner hereindescribed there is an increase in the mechanical strength, since theimpact force occasioned by the return of the disc is reduced, due to thefact that the return is spread out over a certain period of time.

Having thus described a single embodiment of the invention, it isobvious that the same is not to be restricted thereto, but is broadenough to cover all structures coming within the scope of the annexedclaims.

What I claim is:

1. A safety device for refrigeration compressors comprising, a cylinderincluding a piston chamber, a pressure chamber and a suction chamber, aseat in the cylinder, a disc movable to and from the seat having a lowerend for seating against the seat, spring means for urging the disctoward the seat, said disc having a head carried by it and having itsperimeter spaced inwardly of the lower end of the disc and thus definingan annular spacing between its perimeter and the lower part of the disc,which spacing establishes communication between the pressure chamber andthe piston chamber, a plate movably mounted on the disc, said platebeing apertured, spring means for urging the plate toward the head, thehead being apertured, pressure valves arranged between the head andplate and effective to close the apertures in the head when the plate isurged toward the head and also effective at that time to close thespacing between the perimeter of the head and the lower end of the disc,the disc when raised from its seat by refrigerant surge being effectiveto establish communication between the pressure chamber and the suctionchamber, while raising of the plate relatively to the head also by saidsurge opens the annular spacing between the head and the disc and thus,establishes communication between the piston chamber and the pressurechamber.

2. A safety device for refrigeration compressors comprising, a cylinderhaving a piston chamber, a pressure chamber and a suction chamber, apiston movable in the piston chamber, a movable disc interposed betweenthe piston chamber and the pressure chamber, a seat in the cylinder forreceiving the movable disc, the disc having an apertured head carried byit at one end, which head defines an annular spacing between itsperimeter and a part of the disc, the disc including a spider at its endremote from the head, a spring operative against the spider to seat thedisc, a plate encircling the disc between the spider and head, saidplate being of a diameter to cause it to close the annular spacing, saidplate having apertures extending through it, pressure valves interposedbetween the plate and the head, said valves being effective to close theapertures through the head and to also close the annular spacing whenthe disc is seated and the plate is urged toward the head, and springmeans interposed between the'plate and the spider and acting to bias theplate toward the head, the plate and disc when elevated by refrigerantsurge serving to respectively es tablish communication between thepressure chamber and the suction chamber and between the piston chamberand the suction chamber.

3. A safety device for refrigeration compressors comprising, a cylinderhaving a pressure chamber and a suction chamber, a piston movable in thecylinder toward the pressure chamber, a spring-loaded disc disposedbetween the top of the piston and the pressure chamber, a seat in thecylinder toward and against which the disc is urged by its spring, saiddisc including an apertured head carried by it free of contact with theseat, a plate carried by the disc above the head, said plate carryingpressure valves interposed between it and the head and effective tocloses the apertures in the head when the plate is urged toward thehead, the head and a part of the disc defining an aperture between themwhich is also closed by the pressure valves when the plate is urgedtoward the head, the plate having apertures communicating with those inthe head when the plate member is urged away from the head byrefrigerant surge, which surge will also move the disc from its seat toestablish communication between the pressure chamber and the suctionchamber, and spring means for normally urging the plate member towardthe head.

References Cited in the file of this patent UNITED STATES PATENTS839,331 Stevens Dec. 25, 1906 1,475,826 Hoffman Nov. 27, 1923 1,907,478Sutton et a1 Mar. 14, 1933 FOREIGN PATENTS 317,179 Great Britain Mar.20, 1929 50,679 Netherlands Apr. 25, 1938

1. A SAFETY DEVICE FOR REFRIGERATION COMPRESSORS COMPRISING, A CYLINDERINCLUDING A PISTON CHAMBER, A PRESSURE CHAMBER AND A SUCTION CHAMBER, ASEAT IN THE CYLINDER, A DISC MOVABLE TO AND FROM THE SEAT HAVING A LOWEREND FOR SEATING AGAINST THE SEAT, SPRING MEANS FOR URGING THE DISCTOWARD THE SEAT, SAID DISC HAVING A HEAD CARRIED BY IT AND HAVING ITSPERIMETER SPACED INWARDLY OF THE LOWER END OF THE DISC AND THUS DEFININGAN ANNULAR SPACING BETWEEN ITS PERIMETER AND THE LOWER PART OF THE DISC,WHICH SPACING ESTABLISHES COMMUNICATION BETWEEN THE PRESSURE CHAMBER ANDTHE PISTON CHAMBER, A PLATE MOVABLY MOUNTED ON THE DISC, SAID PLATEBEING APERTURED, SPRING MEANS FOR URGING THE PLATE TOWARD THE HEAD, THEHEAD BEING APERTURED, PRESSURE VALVES ARRANGED BETWEEN THE HEAD ANDPLATE AND EFFECTIVE TO CLOSE THE APERTURES IN THE HEAD WHEN THE PLATE ISURGED TOWARD THE HEAD AND ALSO EFFECTIVE AT THAT TIME TO CLOSE THESPACING BETWEEN THE PERIMETER OF THE HEAD AND THE LOWER END OF THE DISC,THE DISC WHEN RAISED FROM ITS SEAT BY REFRIGERANT SURGE BEING EFFECTIVETO ESTABLISH COMMUNICATION BETWEEN THE PRESSURE CHAMBER AND THE SUCTIONCHAMBER, WHILE RAISING OF THE PLATE RELATIVELY TO THE HEAD ALSO BY SAIDSURGE OPENS THE ANNULAR SPACING BETWEEN THE HEAD AND THE DISC AND THUS,ESTABLISHES COMMUNICATION BETWEEN THE PISTON CHAMBER AND THE PRESSURECHAMBER.